Charge transfer transversal filters are well known in the art and are utilized in a variety of digital filtering applications. These devices are essentially discrete time sampled tapped analog delay lines. Predetermined mathematic weighting coefficients are assigned to each tap to provide a filter having predetermined characteristics with a finite impulse response. Node voltages which correspond to each tap are non-destructively sensed and combined with the weighting coefficients, then these voltages are summed to provide an output voltage. Each time the analog voltages are moved under clock control to a new tapped position, an output voltage is again computed, producing an output signal which is dependent upon the transfer function of the filter.
In a charge-coupled device (CCD), an input signal is iteratively sampled at a predetermined frequency f.sub.s. Charge packets proportional to the amplitude values of the samples are formed in a potential well in the semiconductor material adjacent to a sampling gate, and these charge packets are moved from well to well along the CCD channel under the control of clock pulses which occur at a frequency f.sub.c. Before a new sample can be taken each time, the first potential well must be cleared of the charge packet corresponding to the previous sample. Thus the clock frequency f.sub.c becomes a limiting factor for both sampling rate and operating speed of a single channel CCD. Correspondingly, since the minimum sampling rate, or Nyquist sampling rate, must be at least twice the frequency of the input signal, the frequency of the input signal is also limited.